Pressure sensitive hone



Jan. 9, 1968 H. A. FEATHER PRESSURE SENSITIVE HONE 2 Sheets-Sheet 1 Filed March 11, 1965 Harry A. Feather BY INVENTOR.

ATTORNEY.

AGENT.

Jan. 9, 1968 H. A. FEATHER PRESSURE SENSITIVE HONE 2 Sheets-Sheet 2 Filed March 11, 1965 R a m w u: m m V m A w m M 9m .W OAAAHIIWWN\ ww m QE /E Q fig 6v i ...S Q R R mm Q6 v k \SEY 1% 731% winging m mm mm W Qw AGENT.

United States Patent 3,362,113 PRESSURE SENSITIVE HONE Harry A. Feather, Washington, D.C., assignor to the United States of America as represented by the Secretary of the Navy Filed Mar. 11, 1965, Ser. No. 439,108 Claims. (Cl. 51-355) ABSTRACT OF THE DISCLOSURE A gun bore hone having a length of steel conduit with a longitudinal expanding flap in which conduit there is a rubber tube connected to a source of regulated fluid pressure. A sheet of abrasive material is secured around the outside of the conduit, and the entire assembly is rotated by an electric motor.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The invention relates to art of finishing internal bores. More particularly, the invention relates to a honing tool adapted for finishing bores of relatively small diameter with extreme accuracy.

This invention has particular utility in the finishing of the bores of hypervelocity gun barrels, although it will be understood that its utility is not limited thereto. These guns are used to launch models of missiles in free flight for aeroballistic measurements. The model is normally assembled in a sabot which supports the model in the gun during the launching thereof. Occasionally, the model or the sabot will fail during the launching procedure and when this happens, metallic components of the model may come into contact with the bore. Damage usually occurs as scratches or grooves in the bore. These scratches or grooves permit gas leakage past the sabot seal cup or cause damage to the sabot itself upon subsequent firing, and therefore cannot be tolerated.

Conventional honing devices such as conventional brake cylinder homes have been found to be unsatisfactory for the present purposes. These devices have three flat stones, approximately 4 inches long, which stones are supported at 120 intervals and biased outwardly by means of a mechanical or hydraulic system. The device is normally provided with a chuck to permit driving it at a slow speed with an electric motor. Much difliculty was experienced in the attempts to use this kind of abrading device. Because of the arrangement of the stones, convolutions and ovality occurred in the barrel. Due to the shortness of the stones, a constant bore size was diflicult to maintain. Moreover, in the hands or" an expert machinist, the time required for reconditioning a moderately damaged bore was from 4 to 8 hours of honing time.

Accordingly, it is an object of this invention to provide a honing device which does not suffer from the disadvantages above-mentioned, but which is simple in construction, easy to handle, and which provides a constant bore size, a true circular cross-section and which improves the straightness of the bore.

It is further an object of the invention to provide a honing device Which is effective to reduce the time required to refinish a damaged bore, and which may be so used by personnel who are not skilled in the use of machine tools.

Still another object of the invention is to provide a honing tool which is fully portable so as to 'be applicable to a gun barrel in place.

Briefly described, the invention consists of an elongated steel tube provided with an expanding flap on one side. Means are provided to connect the steel tube to a motor to rotate the tube at a preselected speed. A rubber tube is provided inside the body of the steel tube which communicates in any suitable manner with a source of regulated fluid pressure Which operates to expand the flap. A sheet of flexible abrasive paper or cloth is fitted around the body of the steel tube. This structure provides a long honing surface, which contributes to the straightening effect; places a large surface area of abrasive in contact with the bore which aids in keeping the bore round; and is extremely sensitive to variations in bore diameter. The time required for removing moderate damage has been greatly reduced and the problems of out-of-round conditions and the problem of size deviation has been minimized. Moreover, these results can be easily achieved by unskilled personnel.

Other objects, advantages, and new features of the present invention will become apparent from a reading of the following detailed description when taken with the accompanying drawings wherein:

FIG. 1 is a schematic view of the honing device of the invention With its associated equipment;

FIG. 2 is a partial perspective view of a first embodiment of the hone according to the invention, with the abrasive material removed for clarity;

FIG. 3 is a cross-section through a second embodiment of a honing head which is applicable to larger bores than the embodiment of FIG. 2;

FIG. 4 is a section taken on line 44 of FIG. 2; and

FIG. 5 is a longitudinal section through still another embodiment of the invention.

Referring now to FIG. 1, a honing head according to the invention is generally shown at 10. The details of head 10 will be discussed below with reference to FIGS. 2 to 5. Head 10 is rigidly coupled, in any suitable manner, to an extension rod 11 which is tubular in form and which may be of any desired length. At its end opposite head 10, extension rod 11 is connected to a suitable electric motor 12, which may be a drill motor for example, and Which is provided with handles 13 and 14 which can be grasped and used to manipulate the device into the bore to be honed. Motor 12 is connected to a suitable source of electric power through a control means 16, which may be used to vary the speed of rotation of the head 10.

As stated above, the honing pressure is controlled and varied by applying fluid pressure to the interior of the honing head. For this purpose the interior of the honing head is connected through the tubular rod extension 11 to a suitable source of fluid pressure, not shown. The fluid pressure source is connected through a pressure regulator 17 to the extension rod 11 by means of a commutating sleeve 18 of conventional construction.

FIG. 2 illustrates one form of honing head according to the present invention. In this embodiment, the honing head comprises a steel cylinder 19 having a rubber tube 20, disposed therein, the interior of tube 20 being in fluid communication with the interior of extension rod 11. Cylinder 19 is provided with an integral expanding flap 21 at one side thereof by cutting the tube to form a longitudinal slot 22 and, arcuately spaced therefrom by about and in parallel relation thereto, a series of relatively short slots 23 having radial slots 23a extending from the ends thereof over an arcuate extent of approximately 45. The material left between the short slots 23 acts as a hinge to permit the radial expansion of flap 21. Radial slots 23a improve the hinging action by spreading the internal strain over a greater volume of metal.

A piece of emery cloth or other flexible abrasive material is Wrapped around the tube 19 and secured thereto. With no pressure applied, the marginal edge of the abrasive can be easily slipped through slot 22 into the zone between the cylinder 19 and rubber tube 20. The pressure can then be applied to clamp the abrasive in place.

The structure of FIG. 2 is suitable for small bores and has been satisfactorily used for a 20 millimeter gun. For larger guns, however, a simple construction such as that of FIG. 2 is not satisfactory since it is not sutficiently rigid and does not permit sufficient movement of the expanding flap. Accordingly, for the purpose of honing larger guns, a construction as illustrated in FIG. 3 will be better. It will be understood that the head according to the FIG. 3 embodiment will be elongated in the same manner as the FIG. 2 embodiment, the essential difference between the two being in the manner of providing the expanding flap. In this embodiment, the main body of the honing head is again a steel cylinder, in this case indicated by reference numeral 24. Cylinder 24 has disposed within it a rubber tube 26. In this embodiment, the tube 26 is of smaller outside diameter than the inside diameter of cylinder 24 so as to define a space between the cylinder and the rubber tube.

An elongated expanding flap 27 is hingedly connected to tube 24 in the following manner. Cylinder 24 is provided with a longitudinally extending slot, generally indicated at 28. A portion 29 of expanding flap 27 is bent generally at a right angle to flap 27 and extends through the slot 28 to the interior of tube 24. Portion 29 is again bent slightly, as indicated at 30, and the marginal edge thereof lies between the tube 26 and the interior of the cylinder 24.

In order to bias flap 27 outwardly, there is provided a pusher plate 31 which extends longitudinally within the cylinder 24 and is in contact with the rubber tube 26. Pusher plate 31 is connected to the expanding flap 27 by means of a plurality of connecting legs 32 which extend out of tube 24 through a plurality of longitudinal slots 33, extending parallel to the slot 28. If desired, the con necting portions 32 may be secured in any suitable manner, as by welding, to the expanding flap 27. Slots 33 should then be made substantially wider than the legs 32 to permit them to tilt.

The construction of the hinge in this embodiment provides a convenient method of securing the abrasive in place on the device. As shown in FIG. 3, the abrasive 34 is shown as having its marginal edge 36 clamped between the marginal edge of the expanding flap 27 and the interior of the tube 24 by means of the pressure within the tube 26 in much the same way as was described for the FIG. 2 embodiment. The cloth is then wrapped around the body of tube 24 and terminates just short of the slot 28.

In some cases, as where bores of larger diameter are to be honed, it may be desirable to provide additional support for the primary, abrasive-supporting cylinder. FIG. 5 illustrates one way in which this can be accomplished. In the embodiment according to this figure, a central tubular rod 37 of rigid, thick walled construction is provided as the central support. Rod 37 may be threaded, as shown at 38, for connection to the drive rod from the motor. The main, abrasive-supporting sleeve 39 in this embodiment is supported on the rod 37 by means of a spacer block 40 of annular form at the end nearest the drive motor, and by an end plug 41 at the opposite end, which may be secured to rod 37 by means of bolt 42. The diameter of end plug 41 may be reduced somewhat, as shown at 43, to provide a seat for the free end 44 of sleeve 39, so as to provide a continuous extension of the outside surface of sleeve 39. In order to transmit torque between the rod 37 and the sleeve 39, pins 46, which may be several in number, may be inserted through tube 39 into the plug 41 into suitable drill holes therein. At the opposite end, the sleeve may be pinned to the rod 37 by means of a pin 47 extending all the way across the diameter of the device. It will be understood that the outside diameter of the pin 47 is smaller than the inside diameter of the bore 48 in rod 37 so as to permit the passage of fluid past pin 47.

The sleeve 39 will be understood to have an expanding flap as described above. In order to provide a means for expanding the flap, the FIG. 5 embodiment utilizes a rubber sleeve 49 disposed in the zone between the external periphery of rod 37 and the inside of sleeve 39. This rubber sleeve 49 has molded thereon at each end thereof internal beads as indicated at 50 and 51, to provide support from rod 37. The thickness of the sleeve 49 is such as to leave an elongated annular air chamber 52 around rod 37. A plurality of radial bores 53 are provided to provide fluid communication between bore 48 in rod 37 and the annular chamber 52. The embodiment according to FIG. 5 has the particular advantage of making it unnecessary for the external sleeve 39 to perform both the functions of transmitting torque and providing support for the entire length of the honing head. Thus, the honing head according to FIG. 5 is more rigid and may be advantageously used in larger bores.

It should be apparent from the above discussion that it is intended that the honing head used in any particular bore have an outside diameter only slightly less than the inside diameter of that bore. While this requirement makes it necessary to provide a different honing head for each bore size contemplated, there are nevertheless particular advantages to be gained. By keeping the hone size close to the bore size, the area of contact between the abrasive and the bore is maximized. Size adjustments can be accomplished very conveniently by applying the abrasive in several layers.

In using the device, the proper outside diameter is first selected and adjusted as indicated above. The honing head is then inserted into the bore which has theretofore been found to be in need of refinishing. It is sometimes necessary to grasp the outside of the honing head and rotate it by hand in order to get it into the bore, since the diameter has been arranged to be so close to the inside diameter of the bore. After the head has been admitted to the bore, the air pressure is applied to expand the flap to thus increase the force between the abrasive surface and the inside of the bore. The motor is then actuated to rotate the honing head.

The pressure which is applied is not critical, as long as the pressure is not so great as to prevent rotation of the honing head. The pressure should be adjusted by the operator to a level where the frictional force between the hone and the bore is just such as to be tolerable by the operator. It will be apparent that if the honing head is stuck in the bore and an attempt is made to actuate the motor, the casing of the motor will tend to rotate. This creates a situation which is quite uncomfortable for the operator.

The honing head with the properly adjusted pressure is then reciprocated in the bore to cover the entire inner surface thereof. The device is quite sensitive to variations in bore diameter and to the presence of irregularities. If the bone has been properly adjusted in a portion of the bore which is clean and without defects, the operator can feel that the head is rotating easily within the bore. If he then moves the bone to a location where the bore is smaller in diameter or where a protrusion is present, the frictional forces will be increased, creating torque in the motor which he can sense. As the defect is abraded away, or as the diameter of the bore is increased to the size desired, the hone turns more freely and the operator will then know that the defect has been removed.

Thus it can be seen that a hone has been described which meets all the requirements set forth in the objects mentioned above. Obviously, many modifications and variations of the invention will be suggested to those skilled in the art by the above description. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as here specifically described.

What is claimed is:

1. A honing tool for finishing internal bores comprising:

an elongated hollow tubular abrasive support member, said support member having a separate elongated radially movable element hinged to said support member and a flexible abrasive secured therearound,

means for rotating said support member,

means for supplying fluid under regulated pressure to the interior of said support member, and

means for transmitting fluid pressure to said radially movable portion to bias the same outwardly to carry said abrasive into regulatable contact with the bore being honed.

2. A honing tool for refinishing internal bores comprising:

a honing head consisting of an elongated cylinder, a rubber tube disposed Within said cylinder, a separate expanding flap element hinged to said cylinder and a sheet of flexible abrasive material surrounding and secured to said cylinder, the diameter of said head being adjusted to be substantially equal to the nominal diameter of the bore to be honed,

a tubular drive rod connected to said honing head,

an electric motor connected to said drive rod to rotate the same, and

means to supply fluid under pressure to the interior of said tubular drive rod and then to the interior of said honing head,

said expanding flap being radially movable in response to fluid pressure Within said rubber tube.

3. A honing tool as recited in claim 2 wherein:

said cylinder has a elongated longitudinal slot therein,

said expanding flap having a portion thereof bent at substantially a right angle thereto and disposed within said slot, a second portion of said flap being bent to dispose the marginal edge of said portion between the rubber tube and the interior of the cylinder, a plate Within said cylinder in contact with said rubber tube and connecting means extending from said plate 5 through an opening in said cylinder into contact with said expanding flap, said flexible abrasive being secured to said cylinder with the marginal edge thereof clamped between said marginal edge of the bent portion of the flap and the interior surface of said cylinder.

10 4. A honing tool as recited in claim 3, further comprising:

a tubular support rod within said cylinder, and spacer means for rigidly connecting said cylinder to said tubular support rod.

5. A honing tool as recited in claim 4 wherein: the interior of said tubular support rod is in fluid communication with the interior of said drive rod, and said tubular support rod is provided with a plurality of radial bores for establishing fluid communication to the interior of said rubber tube.

References Cited UNITED STATES PATENTS 1,120,023 12/1914 Oangen 51-3 60 2,259,685 10/1941 Elso 5l364 X 2,605,594 8/1952 Macdonell 51373 2,988,859 6/1961. Chafley 51-349 3,178,863 4/1965 Mikiya 51373 3,202,432 8/1965 Cameron.

3,232,011 2/ 1966 Pineau.

ROBERT C. RIORDON, Primary Examiner.

D. G. KELLY, Assistant Examiner. 

